JP2001168462A - Semiconductor multilayer film reflecting mirror and semiconductor light-emitting element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor multilayer film reflecting mirror herein a high reflectivity is kept, while reducing the resistance. SOLUTION: A semiconductor multilayer film reflecting film comprises a first semiconductor layer of a p-type conductive Alx1Ga1-x1As, a second semiconductor layer 5 of p-type conductive Alx2Ga1-x2As, and a third semiconductor layer of a p-type conductive Alx3Ga1-x3As, with the first and third semiconductor layers 3 and 7 alternately laminated with the second semiconductor layer 5 in-between. He composition of Al of the first -third semiconductor layers is 0<=x1<0.2, 0.8<x3<=1.0, and [0.15(x3-x1)+x1]<x2< [0.4(x3-x1)+x1].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor multilayer mirror, a semiconductor light emitting device using the same, and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a semiconductor light emitting device which can be manufactured collectively by the planar technology and which enables high-density integration, there is a surface emitting laser which emits light in a direction perpendicular to a substrate. Above all, a so-called vertical cavity surface emitting laser, which forms a laser resonator in a direction perpendicular to the substrate, has attracted attention in terms of the degree of freedom of in-plane arrangement and the stacking and integration. Even when viewed as a single laser, a vertical resonator is excellent in single-wavelength characteristics and can obtain a circular narrow emission beam, and thus is also excellent in coupling efficiency with other optical devices.

In a vertical cavity surface emitting laser, in order to improve the oscillation threshold (ie, lower the oscillation threshold), it is necessary to increase the reflectivity of two mirrors constituting the optical resonator as much as possible. Is desirable. In particular, it is desirable that the reflecting mirror on the light emitting side absorbs little light and the reflecting mirror on the heat sink side has excellent heat dissipation.

By the way, it is known that when two types of thin films having different refractive indices are alternately stacked, a low reflectance and a high reflectance can be obtained. The semiconductor multilayer reflector uses this property in a semiconductor. In recent years, molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD)
Introduced a crystalline length method with excellent film thickness controllability, such as
A high-quality semiconductor multilayer film reflecting mirror can be formed. The semiconductor multilayer mirror can be formed continuously during crystal growth, and a current can flow if impurities are doped to control conductivity.

FIG. 7 is a sectional view showing the structure of a conventional semiconductor multilayer film reflecting mirror 80. In this conventional example, p-type GaAs
An AlAs layer having a different refractive index n (n =
2.97) 83 and a Ga _0.9 Al _0.1 As layer (n =
3.52) Heterojunctions with 85 are alternately stacked. The reflectivity of the semiconductor multilayer mirror depends on the number of pairs of the AlAs layer 83 and the Ga _0.9 Al _0.1 As layer.

FIG. 8 is a graph showing the relationship between the number of pairs and the reflectance of the semiconductor multilayer reflective film of FIG. It can be seen from the graph of FIG. 8 that a high reflectance of 95% or more can be obtained with about 15 pairs of multilayer films. The low refractive index layer shown in FIG.
Not limited to lAs, AlGaAs having a large AlAs mixed crystal ratio
Can also be used. The number of stack pairs is determined by the required reflectivity.

[0007]

However, such a multilayer structure has a large number of interfaces having high hetero barriers. For this reason, the semiconductor multilayer mirror has high conduction resistance despite high reflectivity, and generates heat. As shown in FIG. 8, the reflectance increases as the number of stacked pairs increases,
As a result, the resistance increases, and the current hardly flows. That is, when the semiconductor multilayer mirror is used for the semiconductor light emitting device, it can be said that the conduction resistance of the light emitting device and the reflectance of the semiconductor multilayer film have a trade-off relationship. Further, there is also a problem that light emission characteristics deteriorate due to heat generation due to high resistance, and the life of the semiconductor laser is shortened. Further, in the p-type semiconductor multilayer film region, the activation rate of the acceptor impurity is generally low, and the resistance thereof is considerably higher than that of the n-type. For this reason, the above-mentioned problems become particularly remarkable in a p-type semiconductor multilayer film reflecting mirror.

Accordingly, a first object of the present invention is to provide a semiconductor multilayer film reflecting mirror capable of reducing the resistance of a p-type semiconductor multilayer film and maintaining a high reflectance.

A second object of the present invention is to provide a semiconductor light emitting device having such a semiconductor multilayer film reflecting mirror and having good light emitting characteristics.

A third object of the present invention is to provide a method of manufacturing a semiconductor multilayer mirror having a low resistance and a high reflectance.

[0011]

In order to achieve the first object, a semiconductor multilayer reflector according to the present invention comprises an intermediate semiconductor layer between a high-refractive-index semiconductor layer and a low-refractive-index semiconductor layer. An AlGaAs layer having a refractive index and a band gap is inserted, and certain conditions are given to the AlAs mixed crystal ratio of these three layers.

More specifically, the semiconductor multilayer mirror according to the present invention comprises a first conductivity type Al _x1 Ga _{1- x1} As (0 ≦ x1
<0.2) and a first conductive type A
l _{x 2} Ga _1-x2 and a second semiconductor layer made of As, the first conductivity type _{Al x3 Ga 1- x3 As (0.8} <x3 ≦
1.0), wherein the first semiconductor layer and the third semiconductor layer are alternately arranged alternately with the second semiconductor layer interposed therebetween. The composition x2 of the semiconductor layer is set to [0.15 (x3−x1) + x1] <x2 <[0.4 (x3−x1) + x1] (1).

The second semiconductor film may include a plurality of sublayers whose composition x2 takes different values within the range of the inequality (1). In this case, the composition x2 of the sublayer may change continuously or stepwise.

The first conductivity type is, for example, a p-type,
By inserting a second layer with an intermediate refractive index and energy gap into a semiconductor multilayer mirror of the type
The resistance of the entire reflecting mirror can be particularly effectively suppressed.

In order to achieve the second object, a semiconductor light emitting device according to the present invention comprises a substrate of a first conductivity type, and a first semiconductor multilayer mirror of the first conductivity type disposed on the substrate. A light emitting layer disposed above the first semiconductor multilayer film reflecting mirror; a second conductive type second semiconductor multilayer film reflecting mirror disposed above the light emitting layer; A contact layer having an aperture for light emission positioned above the mirror is provided, and at least one of the first and second semiconductor multilayer film reflecting mirrors is made of _{Alx1Ga1 -x1As} (0≤x1 <0.
2) a first semiconductor layer composed of Al _x2 Ga _1-x2
A second semiconductor layer made of As and Al _x3 Ga _1-x3
Third semiconductor layer made of As (0.8 <x3 ≦ 1.0)
And the first semiconductor layer and the third semiconductor layer are
Are alternately stacked with the semiconductor layers interposed therebetween. At this time, the composition x2 of the second semiconductor layer is set so as to satisfy the relationship of the above inequality (1).

The first conductivity type is, for example, n-type, and the second conductivity type is p-type. Further, the first conductivity type may be p-type and the second conductivity type may be n-type.

In order to achieve the third object, a method of manufacturing a semiconductor multilayer curtain reflecting mirror according to the present invention comprises the steps of (i) forming a _first conductive type Al _x1 Ga _1-x1 As on a semiconductor substrate. Forming a first semiconductor layer in which the composition x1 satisfies 0 ≦ x1 <0.2; and (ii) forming a first conductive type Al _x2 Ga _1-x2 As on the first semiconductor layer. Forming two semiconductor layers; and (iii) on the second semiconductor layer,
Forming a third semiconductor layer made of Al _x3 Ga _1-x3 As of the first conductivity type and having a composition x3 of 0.8 <x3 ≦ 1.0; (iv) first and third semiconductors Layers,
Repeatedly depositing the second semiconductor layer with the second semiconductor layer interposed therebetween, wherein the composition x2 of the second semiconductor layer satisfies the relationship of the above inequality (1).

In the second semiconductor layer forming step, the second semiconductor layer may be formed as a single layer with a constant value of x2 within the range determined by the inequality (3), or may be formed continuously in the process of forming the second semiconductor layer. Alternatively, it may be formed by changing the composition of x2 stepwise within the range of inequality (3). When the second semiconductor layer is formed by changing the value of x2, it is preferable to form the second semiconductor layer so that the thickness of the second semiconductor layer is substantially equal to the case where the value of x2 is fixed. By doing so, an increase in resistance can be effectively suppressed.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a configuration of a semiconductor multilayer film reflecting mirror 10 according to a first embodiment of the present invention.

The semiconductor multilayer reflector 10 is made of p-type Al.
First semiconductor layer 3 made of _0.15 Ga _0.85 As
A second semiconductor layer 5 made of p-type Al _0.35 Ga _0.65 As and a third semiconductor layer 7 made of p-type AlAs
And the first semiconductor layer 3 and the third semiconductor layer 7 are
They are alternately stacked with the second semiconductor layer 5 interposed therebetween.

In the example of FIG. 1, the Al composition x1 of the first semiconductor layer 3 is set to 0.15, but 0 ≦ x1 <0.
Any value in the range of 2 can be taken. Although the Al composition x3 of the third semiconductor layer 7 is set to 1.0, it is set to 0.1.
Any value in the range of 8 <x3 ≦ 1.0 can be taken. A preferable range of the composition x2 of the second semiconductor layer 5 inserted between the first semiconductor layer 3 and the third semiconductor layer 7 is [0.15 (x3−x1) + x1] <x2 <[0.4 (x3−x1) + X1] (1). That is, the range of x2 determined from the values of x1 and x3 described above is 0.28 <x2 <0.49 (2), and is set to x2 = 0.35 in the first embodiment.

The film thickness of the first semiconductor layer 3 and the third semiconductor layer 7 is 70 nm, and the film thickness of the second semiconductor layer 5 inserted between them is 10 nm. Generally, as the number of semiconductor layers having different refractive indices increases, the reflectivity of the reflector as a whole also increases. However, as the thickness of the reflector increases, the resistance also increases. Therefore, the thickness of the second semiconductor layer 5 which is an intermediate layer interposed therebetween is set to 10 n which is a thickness which does not adversely affect the reflectance of the entire reflecting mirror and can reduce the resistance.
m.

In the first embodiment, the first stacked layers are alternately stacked.
The number of pairs (pairs) of the semiconductor layer 3 and the third semiconductor layer 7 is 20 pairs. The number of such pairs is also selected based on the balance between the reflectance and the resistance of the entire semiconductor multilayer mirror. In the first embodiment, a p-type semiconductor multilayer mirror 1
0 is formed, for example, Zn is used as a p-type dopant, and the carrier density of each layer is set to 2 × 10 ¹⁸ cm.
^-3 .

As described above, by inserting the relatively thin second semiconductor layer 5 having a specific composition between the first semiconductor layer 3 and the third semiconductor layer 7, two different reflectivity p are obtained. It is possible to effectively suppress a sudden increase in resistance when the type semiconductor layers are alternately stacked.

FIG. 2 shows the composition x of the ternary mixed crystal semiconductor Al _x2 Ga _{1 -x2} As constituting the semiconductor multilayer mirror of FIG.
3 is a graph showing the change in resistance R as a function of 2.
In order to check the resistance value R, the IV characteristic is measured on a sample having a relatively large size, and the resistance value is obtained from the slope of the IV characteristic.
It was converted to a resistance value R of a 10 μm square sample.

From the graph of FIG. 2, when the composition x2 satisfies the above inequality (2), the resistance value R of the semiconductor layer is suppressed to a very low value, and when x2 ≒ 0.35, the resistance R is minimized. It turns out that it becomes. Thus, the value of x2 is determined by the Al composition x1 of the first semiconductor layer 3 having a relatively high refractive index,
Al composition x3 of third semiconductor layer 7 having a relatively low refractive index
Is set in the range of the above inequality (1).

Al _0.15 Ga as the first semiconductor layer 3
_{Between the 0.85} As layer and the AlAs layer as the third semiconductor film 7, a low-resistance Al _0.35 Ga _0.65 As film having a composition x2 in the range represented by the inequality (2) is formed as the second By inserting it as the semiconductor layer 5, the resistance value of the p-type semiconductor multilayer mirror as a whole can be effectively reduced.

In the first embodiment, in order to reduce the overall resistance of the multilayer mirror, the reflectance when the second semiconductor layer 5 is inserted into each of the 20 pairs of multilayer stacks is 99.
% Or more. From these results, it can be seen that even when the second semiconductor layer 5 is inserted, no adverse effect that impairs the reflectivity of the reflector formed by laminating the first semiconductor layer 3 and the third semiconductor layer 7 is shown. Understand. When the semiconductor multilayer mirror is used on the light emitting side of a semiconductor light emitting device such as a surface emitting diode, the best reflectance is 97% to 98%. If the reflectance is higher than this, light cannot be extracted efficiently.

FIG. 3 is a view showing a modification of the semiconductor multilayer mirror shown in FIG. In the example of FIG. 3, the intermediate layer (that is, the second semiconductor layer) inserted for the purpose of reducing the resistance is constituted by a plurality of sublayers. Each sublayer has a different value of composition x2. In the example of FIG. 3, the first semiconductor layer 3
Semiconductor layer 5 inserted between the first semiconductor layer 7 and the third semiconductor layer 7
Are the first sublayer 51 and the second sublayer 5
Consists of two. Al composition x of first sublayer 51
Set 2 to _{0.34 (Al} 0.34 _{Ga 0.6} 6 A
s), the Al composition x2 of the second sublayer 52 is set to 0.
36 (Al _0.36 Ga _0.64 As). Both values of composition x2 are within the range defined by inequality (1).

When the second semiconductor layer is constituted by the first and second sub-layers, the thickness of the entire second semiconductor layer is 1
It is preferably about 0 nm. This is because if the film thickness is too large, the reflectance of the whole multilayer mirror is adversely affected.

In the example shown in FIG. 3, the second semiconductor layer is composed of two sub-layers. However, the second semiconductor layer may be composed of two or more sub-layers by changing the value of the composition x2 of Al stepwise. . Further, the second semiconductor layer may be formed by continuously changing the value of x2 within the range of the inequality (1). In any case, the resistance value of the entire semiconductor multilayer film reflecting mirror can be effectively reduced.

As described above, since the heat generation is suppressed by reducing the resistance value of the semiconductor multilayer film reflecting mirror, the effect of extending the life of the semiconductor multilayer film reflecting mirror is obtained. Furthermore, if this semiconductor multilayer film reflecting mirror is used for a semiconductor light emitting device, heat generation is suppressed, so that the heat generation characteristics of the semiconductor light emitting device are improved and the life of the semiconductor light emitting device is prolonged.

FIGS. 4 and 5 are views showing the configuration of a surface emitting laser according to a second embodiment of the present invention. FIG. 4 is a sectional view and FIG. 5 is a plan view. This surface emitting laser uses the semiconductor multilayer film reflecting mirror described in the first embodiment for at least one of the substrate side reflecting mirror and the light emitting side reflecting mirror.

As shown in FIG.
A first reflection mirror (substrate-side reflection mirror) 103 disposed on the n-type substrate 101 via a buffer layer (not shown), and made of an n-type semiconductor multilayer film; A light-emitting layer 105 disposed above the mirror 103;
5 and is formed of a p-type semiconductor multilayer film.
Reflecting mirror (light emitting side reflecting mirror) 107 and second reflecting mirror 107
And a wiring electrode (anode electrode) 113 having an aperture for light emission. Although not shown, a cathode electrode is connected to the back surface of the n-type substrate 101. At least one of the first and second reflecting mirrors (both in the second embodiment) is Al _{x 1} Ga
_{A first} semiconductor layer made of _1-x1As , and _Alx3Ga
A third semiconductor layer made of _1-x3 As and Al _{x 2} Ga
It has a multilayer structure in which a second semiconductor layer made of _1-x2 As is repeatedly arranged with a second semiconductor layer interposed therebetween. The Al compositions of the first to third semiconductor layers are selected so as to satisfy the above inequalities (1) to (3).

By constituting a reflecting mirror with a semiconductor multilayer film having such a composition, the resistance can be reduced and the emission characteristics of the surface emitting laser 100 can be improved.

FIG. 5 is a plan view of the surface emitting laser 100. Since the surface emitting laser 100 is of a vertical resonator type in which two reflecting mirrors formed in the vertical direction form an optical resonator, the element size can be reduced to about 10 μm. Light emitted by the light emitting layer and amplified by dielectric emission is extracted from the light emitting region surrounded by the polyimide 109 in a direction perpendicular to the substrate. Therefore, the degree of freedom of arrangement when a two-dimensional array is formed by the surface emitting laser 100 is large.

FIG. 6 shows a manufacturing process of the surface emitting laser 100.
FIG. First, as shown in FIG.
an n-type first reflecting mirror 103 on an aAs substrate 101;
The layer 105 and the p-type second reflecting mirror 107 are formed by MOCVD.
In some cases, continuous epitaxial growth is performed. n-type first counter
The projection mirror 103 and the p-type reflection mirror 105 are made of Al_x1Ga
_1-x1A first semiconductor layer made of As and Al_x3Ga
_1-x3A third semiconductor layer made of As with Al_x2
Ga_1-x2Repeatedly sandwiching the second semiconductor layer made of As
It is formed by back lamination. At this time, the first
-Al composition x1, x2, x3 of the third semiconductor layer is not
It is set so as to satisfy the equations (1) to (3). A
For example, the composition of l
・ By adjusting with a controller (MFC)
Be changed.

The number of pairs of the first reflecting mirror 103 is 37, and the number of pairs of the second reflecting mirror 105 is 20. The reason why the number of pairs of the first reflecting mirror 103 is larger than the number of pairs of the second reflecting mirror 105 is that the first reflecting mirror 103 is formed of an n-type semiconductor multilayer film, so that the number of stacked layers is increased. This is because the increase in resistance caused by the p-type multilayer film is not so remarkable. Also, because the first reflecting mirror 103 is on the substrate side, it is not necessary to consider the ease of light extraction, and it is preferable to achieve a reflectance of about 99%.

The n-type dopant of the first reflecting mirror 103 is, for example, silicon (Si).
The type dopant is, for example, zinc (Zn). The carrier densities are both 1 × 10 ¹⁸ cm ⁻³ .

The light emitting layer 105 is formed of, for example, GaAs active
The region is p-type and n-type Al_yGa _1-ySandwiched between As
It is a double heterojunction layer. P-type and n-type light emitting layers
Al _yGa_1-yThe composition y of the As layer is 0.3,
The degree is 2 × 10¹⁷cm^-3It is.

After the continuous epitaxial growth, the surface of the epitaxially grown layers (103, 105, 107) is covered with a photoresist 120.

Next, as shown in FIG. 6B, the photoresist 120 is exposed by photolithography using a mask having a pattern of a polyimide region 109 surrounding the light extraction region, and an etching mask of the photoresist 120 is formed. To form Then, using this etching mask 120, reactive ion etching (RI
A groove for embedding the polyimide is selectively formed by E) or the like.

In the step of FIG. 6C, the annular groove formed in the previous step is filled with polyimide to form a polyimide region 109.
Is formed, and the photoresist is removed.

Thereafter, as shown in FIG.
An SiO ₂ protective film 111 covering the second reflecting mirror 107 and the polyimide 109 is formed by a method or the like. Further, a photoresist 120 is spin-coated on the protective film 111.

In FIG. 6E, the photoresist 120 is exposed using a mask having a pattern of the wiring electrode 113, and a window for forming an electrode is formed in the photoresist 120.

Finally, as shown in FIG. 6F, Au or Au-
Be is deposited by sputtering or vacuum deposition. afterwards,
A pattern of the wiring electrode 113 serving as an anode electrode is formed by a lift-off process for removing the photoresist 120. Further, Au is applied to the entire back surface of the GaAs substrate 101.
-Deposit a metal film such as a Ge / Au film to use as a cathode electrode. Thereafter, by performing sintering in an inert gas or a hydrogen (H ₂ ) gas at a predetermined temperature, the surface emitting laser 100 is completed.

[0047]

As described above, according to the semiconductor multilayer mirror of the present invention, a high reflectance is achieved, and at the same time, a high resistance, which is particularly remarkable in a p-type laminated structure, is effectively suppressed. be able to. By keeping the resistance low, heat generation can be suppressed, and the life of the reflector can be extended.

Further, when such a semiconductor multilayer film is applied to a semiconductor light emitting device such as a surface emitting laser, the resistance at the reflector on the light emitting side is reduced, and the current is made easier to flow. Can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a semiconductor multilayer film reflecting mirror according to a first embodiment of the present invention.

FIG. 2 is a graph showing a resistance value of the semiconductor multilayer mirror shown in FIG. 1 as a function of an Al composition x.

FIG. 3 is a diagram showing a modified example of the semiconductor multilayer film reflecting mirror shown in FIG. 1;

FIG. 4 is a cross-sectional view showing a configuration of a surface emitting laser using the semiconductor multilayer mirror shown in FIG.

5 is a plan view of the surface emitting laser shown in FIG.

FIG. 6 is a diagram showing a manufacturing process of the surface-emitting laser shown in FIG.

FIG. 7 is a cross-sectional view showing a configuration of a conventional semiconductor multilayer film reflecting mirror.

FIG. 8 is a graph showing the reflectivity of a semiconductor multilayer mirror as a function of the number of pairs of semiconductor layers.

[Explanation of symbols]

1 GaAs substrate 3 first semiconductor layer (p-type Al _0.15 Ga _0.85 A
s) 5 second semiconductor layer (p-type Al _0.35 Ga _0.65 A)
s) 7 Third semiconductor layer (p-type AlAs) 10 Semiconductor multilayer film reflector 51, 52 Sublayer of second semiconductor layer 100 Surface emitting laser 103 First reflector 105 Light emitting layer 107 Second reflector 109 Polyimide region 111 SiO ₂ Protective film 113 Wiring electrode

Claims (7)

[Claims] 1. A first conductivity type Al _x1 Ga _1-x1 As
A first semiconductor layer made of (0 ≦ x1 <0.2), a second semiconductor layer made of Al _x2 Ga _1-x2 As having a first conductivity type, and an Al _x3 Ga _{1- made of} a first conductivity type _x3 As (0.8 <x3
≦ 1.0), wherein the first semiconductor layer and the third semiconductor layer are alternately arranged alternately with the second semiconductor layer interposed therebetween. Wherein the composition x2 of the semiconductor layer is [0.15 (x3-x1) + x1] <x2 <[0.4 (x3-x1) + x1]. 2. The semiconductor multilayer mirror according to claim 1, wherein the second semiconductor layer includes two or more sublayers whose composition x2 has different values. 3. The semiconductor multilayer mirror according to claim 2, wherein the composition x2 of the sublayer of the second semiconductor layer changes continuously or stepwise. 4. A substrate of a first conductivity type, a first reflection mirror disposed on the substrate and made of a semiconductor multilayer film of the first conductivity type, and light emission disposed on the first reflection mirror. A second reflector disposed on the light emitting layer, the second reflector comprising a semiconductor multilayer film of a second conductivity type having a conductivity type opposite to the first conductivity type; and And a contact layer having a light emitting aperture, wherein at least one of the first and second reflecting mirrors is made of Al _x1 Ga _1-x1 As (0 ≦ x1 <0.2). It includes a semiconductor layer, a second semiconductor layer made of _Al x2 _{Ga 1-x2} as, a third semiconductor layer made of _{Al x3 Ga 1-x3 as (} 0.8 <x3 ≦ 1.0), First semiconductor layer and third
Are alternately arranged with the second semiconductor layer interposed therebetween, and the composition x2 of the second semiconductor layer is [0.15 (x3−x1) + x1] <x2 <[0.4 (x3− x1) + x1]. 5. The semiconductor light emitting device according to claim 4, wherein said semiconductor light emitting device is a surface emitting laser. 6. A first conductivity type Al _x 1 on a semiconductor substrate.
Forming a first semiconductor layer made of Ga _1-x1 As (0 ≦ x1 <0.2); and forming the first conductivity type Al _x2 G on the first semiconductor layer.
forming a second semiconductor layer made of a _1-x2 As; and forming the first conductivity type Al _x3 G on the second semiconductor layer.
a _1-x3 As (0.8 <x3 ≦ 1.0)
Forming the second semiconductor layer on the first third semiconductor layer; and forming a first semiconductor layer and a third semiconductor layer between the first and third semiconductor layers. And repeatedly depositing while sandwiching the second semiconductor layer, wherein the composition x2 of the second semiconductor layer is [0.15 (x3−x1) + x1] <x2 <[0.4 (x3−x1) + x1]. A method for manufacturing a semiconductor multilayer curtain reflector. 7. The method according to claim 6, wherein the step of forming the second semiconductor layer is performed while changing the composition x2 continuously or stepwise.